The present invention relates generally to a piezoelectric actuated fuel injector for use in conjunction with an internal combustion engine and, more particularly, to a hydraulic intensifier assembly for interfacing between a piezoelectric actuator and an injector valve of the fuel injector, where the injector valve axially separates from a discharge outlet in response to longitudinal expansion of the piezoelectric actuator, thereby allowing fuel flow from the fuel injector.
Piezoelectric elements are attractive candidates as actuator devices for injector valves in common rail fuel injectors. The precise longitudinal deflection characteristic of piezoelectric devices in conjunction with their rapid dynamic response provides the potential of achieving meaningful control over the rate of fuel injection. Additionally, the relative high load capability of piezoelectric elements is consistent with the extremely high pressure environment of common rail fuel injectors.
Generally, a piezoelectric element will experience longitudinal growth when a voltage is applied to it. In this way, the piezoelectric element may be used to actuate the injector valve of a fuel injector. In a known piezoelectric actuated fuel injector, the longitudinal growth of the piezoelectric element actuates the injector valve to a closed position. When the applied voltage is discharged, the piezoelectric element returns to its initial length, thereby actuating the injector valve to an open position.
However, a piezoelectric element exhibits electrical characteristics similar to those of a capacitor. In other words, its operational life is proportional to the time an electric charge is applied to the piezoelectric element. In the above-described configuration, the operational life is significantly reduced by having to apply voltage to the piezoelectric element in order to retain the injector valve in a closed position. Therefore, it is desirable to provide a hydraulic assembly for interfacing between the piezoelectric element and the injector valve, where the longitudinal expansion of the piezoelectric actuator axially separates the injector valve from its valve seat. In other words, no voltage is applied to the piezoelectric element when the injector valve is in a closed position.
In accordance with the present invention, a piezoelectric actuated fuel injector is provided for use in conjunction with an internal combustion engine. The fuel injector includes a piezoelectric actuator for actuating an injector valve, and a hydraulic assembly for interfacing between the piezoelectric actuator and the injector valve, where the injector valve axially separates from a discharge outlet in response to longitudinal expansion of the piezoelectric actuator, thereby allowing fuel flow from the fuel injector.
For a more complete understanding of the invention, its objects and advantages, refer to the following specification and to the accompanying drawings.